The Simon Communities has seen a 33% increase in those availing of its services.
The 11,000 person increase includes 3,000 children in 1,500 families, according to their latest annual report which is being launched today.
Niamh Randall, National Spokesperson for the Simon Communities, said Christmas is a time of particular concern for people who are homeless.
'We have to be clear this is an emergency based response and while we need to ensure everyone can access a bed, we also need to have a longer term housing led approach.' #simonannualreport
— Simon Communities (@SimonCommunity) December 19, 2017
"What we're really concerned about is the fact that 8,500 people will be trapped in emergency accommodation this Christmas, but also many thousands more will be living in housing insecurity," she said.
"They won't know what's going to happen them after Christmas, they don't know what's happening next year and they have nowhere to go," she added.